Monomer resin

ABSTRACT

The present invention provides an ionomer resin prepared by additionally neutralizing 2 to 30% of free carboxyl groups with magnesium hydroxide. According to the present invention, physical properties of the sodium neutralized ionomer resin are improved.

DESCRIPTION

1. Technical Field

The present invention relates to an ionomer resin which is modified byadditionally neutralizing with magnesium free carboxyl groups in anionomer resin which has been neutralized with sodium.

2. Background Art

Ionomer resins are polymers having ion crosslinking in their chemicalconstitution. The ionomer resins are generally used for cover materialfor rubber articles, wrapping material, the sole of ski boots, carbumpers and the like, because of the excellent toughness and highresilience exhibited thereby.

The ionomer resins may be industrially prepared by a solution method(see Japanese Patent Publication (examined) Nos. 6810/1964 and31556/1974). Japanese Patent Publication (examined) Nos. 15769/1967 and38441/1983 also disclose a method using an extruder. In the abovementioned methods for preparing the ionomer resins, a copolymer of anα-olefin with an α,β-ethylenically unsaturated carboxylic acid or anester thereof is neutralized with a metal ion, such as sodium ion, zincion and the like.

The ionomer resin neutralized with a sodium ion (hereinafter referred toas "sodium neutralized ionomer resin") is superior to the zinc ormagnesium neutralized ionomer resin in rebound properties, but has poordurability at a low temperature, which brings about cracking at atemperature of less than -5 ° C. In order to avoid the above defects, amethod is proposed wherein the sodium neutralized ionomer resin isblended with the zinc neutralized ionomer resin. However, since the typeof the ionomer resin to be blended is very limited, it is difficult toapply the product to a wide variety of products. Another ionomer resincontaining both zinc ion and magnesium ion is proposed in JapanesePatent Publication (examined) No. 38441/1983. This ionomer resin hasexcellent durability at a low temperature, but has poor reboundproperties. This ionomer resin is prepared by using a combination of awater-insoluble metal compound, such as zinc oxide, magnesium oxide,magnesium hydroxide and the like, with a volatile organic acid salt,such as zinc acetate, magnesium formate and the like. The volatileorganic acid salt, however, corrodes the screw of an extruder andtherefore the method is not preferred in an industrial application.

U.S. Pat. No. 4,526,375 discloses a method in which a sodium neutralizedionomer resin is further neutralized with magnesium oxide. The ionomerresin prepared by this method has fairly good physical properties, suchas durability at a low temperature. In the process of preparing theionomer resin, magnesium oxide remains in the obtained ionomer resinwithout participating in the neutralizing reaction. The nonreactedmagnesium oxide is reacted with the ionomer resin when the resin isheated to an elevated temperature in the preparation of the finalproduct. Reaction water is also evolved during the reaction and resultsin the poor durability of the final product. In order to avoid thedefects, it is required to complete the reaction in the preparation ofthe ionomer resin and it takes a long time.

DISCLOSURE OF INVENTION

The inventors of the present invention have found a new preparation ofan ionomer resin. The preparing process is easily carried out using ascrew-type extruder and provides an ionomer resin having excellentdurability at low temperature.

Thus, the present invention provides an ionomer resin prepared byadditionally neutralizing 2 to 30% of the free carboxyl groups of asodium neutralized ionomer resin with magnesium hydroxide.

The sodium neutralized ionomer resin employed in the present inventioncan be a thermoplastic resin prepared by copolymerizing 96 to 70% byweight of a monoolefin with 4 to 30% by weight of an unsaturated mono ordicarboxylic acid having 3 to 8 carbon atoms or an ester thereof (% isbased on total weight of monomer), and neutralizing with sodium.

The sodium neutralized ionomer resins are available from Mitsui Du PontPolychemical Company as HI-MILAN, for example, HI-MILAN 1601, 1605 and1707.

Neutralization with magnesium hydroxide is carried out by mixing thesodium neutralized ionomer resin and magnesium hydroxide by using aroll, a banbury type mixer and an extruder. The extruder is morepreferred because the ionomer resin has an tendency to adhere the metalsurface in the roll or banbury type mixer.

A neutralizing reaction of the free carboxyl group with the magnesiumion may be confirmed by an infrared spectrum in which an absorption of1,700 cm⁻¹ based on --COOH in the ionomer resin is weakened, anabsorption of 1,560 cm⁻¹ based on --COOM (M=Na, Mg) becomes strong andan absorption of 1,600 cm⁻¹ based on --COOMg appears.

When the neutralizing reaction is finished, the resin turns totransparent from white. The ionomer resin after completion of thereaction has a reduced melt index. It is also confirmed by an X-raymicro analyzer that the magnesium ion is uniformly dispersed in theionomer resin.

Magnesium hydroxide is consumed in a short period of time by thereaction and therefore raises no corrosion problems with regard to ascrew cylinder and the like.

When many magnesium compounds are studied by the inventors, it has beenfound that there are noticeable differences between magnesium compoundsin their reactivity. The reactivity of the magnesium compounds is in theorder of magnesium acetate>magnesium hydroxide>magnesium oxide. Themagnesium acetate is not preferred because of corrosion properties andthe magnesium oxide is also not preferred because of poor reactivity.The magnesium hydroxide has suitable properties and can produce themodified ionomer resin of the present invention by passing the resinthrough the extruder once. The magnesium hydroxide may be present in anamount sufficient to neutralize 2 to 30% of the free carboxyl group inthe sodium neutralized ionomer resin. For example, an amount ofmagnesium hydroxide is 0.2 to 1.5 parts by weight based on 100 parts byweight of the sodium neutralized ionomer resin. The amount of magnesiumhydroxide is more preferably about 0.3 parts by weight based on 100parts by weight of the ionomer resin.

In addition to magnesium hydroxide, other additives, such as a pigment,a lubricant, a dispersant, an antioxidant, a stabilizer and anultraviolet absorber can be added to the ionomer resin.

A portion of the sodium neutralized ionomer resin may be pre-reactedwith magnesium hydroxide to form a masterbatch.

INDUSTRIAL APPLICABILITY

The modified ionomer resin obtained as mentioned above is very suitablefor a variety of sporting goods. If the modified ionomer resin isapplied to a golf ball cover, a golf ball core may be covered with twosemi-spherical shells formed from the modified ionomer resin and pressedat an elevated temperature. The modified ionomer resin may cover thecore by an injection molding method.

The golf ball covered with the modified ionomer resin of the presentinvention exhibits excellent durability at a low temperature and doesnot crack at a temperature of -30° C. The golf ball also has good nomaldurability, such as excellent cut-resistance. It, further, has goodanti-aging properties.

BRIEF EXPLANATION OF THE DRAWINGS

FIG. 1 shows an IR spectra of HI-MILAN 1605 which is not neutralizedwith magnesium ion and HI-MILAN 1605 which is neutralized withmagnesium. In FIG. 1, a solid line shows the former and a dotted lineshows the latter.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention is illustrated by the following examples.

EXAMPLE 1

A sodium neutralized ionomer resin HI-MILAN 1605, 1707 available fromMitsui Du Pont Polychemical Company) and a magnesium compound werecharged in a Bent type extruder having a screw and extruded at 226° C.(nozzle size=50 mm φ, L/D=28, vacuum degree=680 mmHg) to form pellets.The pellets were charged in an injection molder and a core of a twopiece golf ball was covered with the modified ionomer resin to form atwo piece golf ball. A melt index value of the modified resin andphysical properties of the obtained golf ball are shown in Table 1.

For a comparison, a combination of HI-MILAN 1605 and 1707, which is notmodified with the magnesium ion, was employed to form a two piece golfball. The golf ball was tested as mentioned above to show in Table 1.The number of the tested golf balls was 12.

Further, IR spectra of HI-MILAN 1605 which are not neutralized with themagnesium ion and HI-MILAN which are neutralized with magnesium, areshown in FIG. 1. In FIG. 1, a dotted line shows the neutralized one anda solid line shows the non-neutralized one.

                                      TABLE 1                                     __________________________________________________________________________                          Example       Comparative example                                              1     2      1      2      3     4                     __________________________________________________________________________    Cover Sodium neu-                                                                           Number  1605   1605/1707 =                                                                          1605   1605/1707 =                                                                          1605  1557/1706 =           formulation                                                                         tralized               60/40         60/40        50/50                       ionomer Metal ion                                                                             Na     Na/Na  Na     Na/Na  Na    Zn/Zn                       resin   Degree of                                                                             29     41     29     41     29    58                                  neutralization                                                        Amount of Mg                                                                          Mg(OH).sub.2                                                                          0.75   0.51   --     --     --    --                          compound                                                                              MgO     --     --     --     --     0.51  --                          Neutralization degree of Mg ion                                                               15     10     --     --     15    --                          Melt index (M.I.)                                                                             1.2    1.0    2.8    2.0    1.4   2.9                   Physical                                                                            Rebound coefficient.sup.a                                                                     0.785  0.784  0.784  0.785  0.783 0.767                 properites                                                                          Durability of   No crack                                                                             No crack                                                                             Two were                                                                             Two were                                                                             (1)   No crack              of golf                                                                             low temperature.sup.b                                                                         at -30° C.                                                                    at -30° C.                                                                    cracked                                                                              cracked      at -30°                                                                C.                    ball                                at -10° C.                                                                    at -20° C.                        Durability of low                                                                             One was                                                                              (2)    All were                                                                             All were                                                                             (3)   No crack                    temperature after leav-                                                                       cracked       cracked                                                                              cracked      at -30°                                                                C.                          ing at 60°  C. for 14 days                                                             at -30° C.                                                                           at -10° C.                                                                    at -10° C.                  __________________________________________________________________________     (1) One was cracked at -10° C. and the remainings were not cracked     at -30° C.                                                             (2) No crack was raised at -10° C. and two were cracked at             -20° C.                                                                (3) One was cracked at -20° C. and four were cracked at -30.degree     C.                                                                       

[Method of test]

hu a Rebound coefficient: Rebound coefficient is calculated from a speedof a golf ball when a cylindrical item having 198.4 g is collided with agolf ball at 45 m/sec.

^(b) Durability of low temperature: After leaving a golf ball at a fixedtemperature over day and night, the ball is collided five times with aboard followed by cooling to the fixed temperature and then collidedanother five times. This is repeated five times.

I claim:
 1. An ionomer resin comprising an ionomer resin productprepared by additionally neutralizing with magnesium hydroxide freecarboxyl groups of a sodium neutralized ionomer resin,said sodiumneutralized ionomer resin being prepared by copolymerizing 96 to 70% byweight of a monoolefin with 4 to 30% by weight of an unsaturated mono-or di-carboxylic acid having 3 to 8 carbon atoms or an ester thereof andneutralizing with sodium, said weight % being based on the total weightof the monomer, wherein said magnesium hydroxide is added to said sodiumneutralized ionomer resin in an amount sufficient to neutralize 20 to30% of the free carboxyl groups in said sodium neutralized ionomer resinand mixing at a temperature of from 150° to 250° C.
 2. The ionomer resinaccording to claim 1, wherein the amount of said magnesium hydroxide is0.2 to 1.5 parts by weight based on 100 parts by weight of said sodiumneutralized ionomer resin.
 3. The ionomer resin according to claim 1,wherein the amount of said magnesium hydroxide is about 0.3 parts byweight based on 100 parts by weight of said sodium neutralized ionomerresin.
 4. A resin product comprising:an ionomer resin according to claim1, and an additive selected from the group consisting of pigments,lubricants, dispersants, antioxidants, stabilizers and ultravioletabsorbers.
 5. A resin product comprising:an ionomer resin according toclaim 2, and an additive selected from the group consisting of pigments,lubricants, dispersants, antioxidants, stabilizers and ultravioletabsorbers.